Load carrying arrangement for a vehicle

ABSTRACT

A loadbearing structure for heavy vehicles, e.g. a freight vehicle, incorporates a box-shaped hollow unit ( 10 ) extending in the longitudinal direction of the vehicle. Wall elements ( 12, 14, 16, 18 ) of thin wall thickness are connected to one another to form the box-shaped unit ( 10 ). The invention provides a loadbearing structure ( 2 ) for heavy vehicles which is many times more rigid than conventional structures but is nevertheless of relatively low weight and is relatively easy and inexpensive to manufacture. The present invention also relates to a process for manufacturing a loadbearing structure for heavy vehicles.

BACKGROUND OF THE INVENTION

The present invention relates to a loadbearing structure for heavyvehicles, e.g. a freight vehicle, and to a process for manufacturing aloadbearing structure for heavy vehicles.

BACKGROUND AND STATE OF THE ART

A known practice for heavy vehicles, e.g. trucks and similar freightvehicles, is to design a loadbearing structure in the form of a vehicleframe. The commonest type of vehicle frame for freight vehicles is aladder type of frame member structure which incorporates a pair ofparallel longitudinal side members. These side members extendsubstantially along the whole length of the vehicle, on opposite sidesof the vehicle. Along the whole length of the side members amultiplicity of transverse members are arranged at intervals and connectthe side members to one another. Such a frame member structure supportsthe driving cab and a load surface, e.g. a load platform or fixed vansuperstructure. The frame member structure also caters for fittingvarious components of the vehicle, e.g. engine, suspension system, wheelshafts etc.

A loadbearing structure in the form of a frame structure for a heavyvehicle serves as the main loadbearing element for achieving strengthand rigidity, unlike buses, for example, in which the whole of thebodywork affects their rigidity and strength. However, a traditionalform of vehicle frame is designed to be relatively bendable andtwistable (herein called torsionable), with the object of being able tocope with heavy loads and varying road conditions, ranging from forestroads or no roads at all to smooth motorways. However, this relativelylow resistance to bending and twisting entails difficulties as regardsthe vehicle's running characteristics. It is also difficult on atorsionable vehicle frame to try to compensate for the vehicle'smoderate running characteristics by installing some kind ofsophisticated suspension system. As transport by heavy vehiclescurrently takes place largely on smooth roads and decreasingly on unevenforest roads and the like, better running characteristics on the latterhave become increasingly important. Frame rigidity greatly influencesthe running characteristics. On a smooth road the runningcharacteristics can be improved by increasing the rigidity of the frame.

When a heavy vehicle with a ladder type of frame member structure has tobe equipped with a load surface in the form of a load platform orpermanent van superstructure, it is usual for U-shaped members to bearranged at the bottom of the frame member structure to render the framemember structure rigid and provide support for the platform or van bodyrelative to the frame members. This causes problems in that a built-onplatform or van body is relatively rigid, whereas the frame memberstructure is torsionable, which means that special fastenings arerequired. U-shaped members for load platforms/van bodies cause anundesirable extra vehicle weight increase.

WO-A2-9414627 describes a loadbearing structure in the form of a vehicleframe for a motor vehicle, which incorporates a tubular extruded sectiondesigned to allow optimum utilisation of the space in the vehicle body.The tubular extruded section is used to accommodate such items asbatteries, which are inserted into it by means of trolleys. Thestructure according to WO-A2-9414627 does not indicate any solution tothe problems described with regard to the above state of the art.

DESCRIPTION OF THE INVENTION

The object of the present invention is to provide a loadbearingstructure for vehicles, preferably heavy trucks, which is significantlymore rigid than conventional structures and obviates said disadvantagesof the state of the art. One object is therefore to provide a structurewhich results in better vehicle running characteristics in the mostcommonly occurring operating situations, which in the case of heavytrucks is relatively smooth roads. A further object is to provide aweight-optimised structure which is easy and inexpensive to manufacture.Another object of the present invention is to provide a structure whichmakes it easy to carry out repairs and servicing both of the frame andof components arranged on it, and to provide a large proportion of saidcomponents with an environment protected against external influences.

To these ends, the invention is a loadbearing structure for heavyvehicles, e.g. a freight vehicle, which incorporates a box-shaped hollowunit extending in the longitudinal direction of the vehicle. Wallelements of thin wall thickness are connected to one another to form thebox-shaped unit. The invention provides a loadbearing structure forheavy vehicles which is many times more rigid than conventionalstructures but is nevertheless of relatively low weight and isrelatively easy and inexpensive to manufacture. The present inventionalso relates to a process for manufacturing such a loadbearing structurefor heavy vehicles.

An advantage of the solution according to the invention is that it makespossible a very torsion-resistant structure with low weight, resultingin better running characteristics, comfort and road holding as comparedwith structures according to the state of the art. It improves rigidityin all directions, but particularly the torsional rigidity. Theloadbearing structure according to the present invention can increasethe torsional rigidity of the vehicle frame by several thousand timesand the bending resistance by about ten times. All the constituentelements of the structure participate in the distribution of forces andincrease the rigidity. The structure according to the present inventionalso makes it possible to achieve a weight-optimised vehicle frame. Italso facilitates repair and servicing work through good accessibilityfrom the underside of the vehicle.

The box-shaped body is advantageously bounded by an upper roof wallelement arranged horizontally, a lower bottom wall element and twovertical wall elements. The respective vertical wall elements and partof the horizontal wall element may advantageously be manufactured anddesigned integrally. This makes it possible to create mutually identicalcomposite sections which are stackable and which also render themanufacturing process easier and more efficient. Two such separateelements which in certain cases are identical can be brought together atassembly stage to form a composite unit with vertical walls and ahorizontal upper wall element. The respective vertical wall elements maythus advantageously be designed with a wall portion arrangedsubstantially vertically which also incorporates part of a horizontalwall element extending from the upper end of the vertical wall element.The wall element thus forms an L-shape. Two opposite L-shaped wallelements placed at a distance from one another are joined together bythe two respective protruding horizontal portions and form incombination with one another a composite unit incorporating the upperhorizontal wall element and the vertical wall elements.

The wall elements for the box-shaped structure may preferably be insheet form and largely consist of corrugated sheetmetal, which is muchmore rigid than entirely planar sheetmetal of the same thickness. Thewall elements consist of material with thin wall thickness with a viewto achieving a weight-optimised loadbearing structure. For applicationon a heavy freight vehicle, the material thickness in the case of sheetsteel may be about 5 mm or less.

According to one embodiment, the box-shaped unit is provided internallywith at least one supporting frame structure. The purpose of such asupporting frame is to reduce the risk of buckling of the constituentwall elements of the box-shaped unit. Advantageously, supporting framestructures are placed within and distributed along the whole of thebox-shaped unit. The larger the number of supporting frames used in thebox-shaped unit, the higher the torsional rigidity of the resultingstructure. On the inside of the box-shaped unit, the respectivesupporting frame structures are firmly connected to the wall elements.Each supporting frame structure is a homogeneous frame, advantageouslyintegral, which has a substantially square shape and a central aperture.The supporting frame incorporates an upper and a lower horizontalelement and, arranged between them, two substantially vertical elementsat a distance from one another. The supporting frame may also have othersuitable geometrical shapes, e.g. rectangular or parallelepipedic. Thethickness and extent of the supporting frame in the longitudinaldirection of the box frame are small relative to the latter's extent inthe width and height directions, i.e. transverse to the extent of thebox-shaped unit in the longitudinal direction.

According to another embodiment, the loadbearing structure incorporatessupporting devices arranged on the outside of the substantially verticalwall elements of the box-shaped unit. These supporting devices areadvantageously placed in the longitudinal direction on the outside anddistributed along substantially the whole of the box-shaped unit. Thesupporting devices have advantageously in the vertical plane an extentwhich corresponds to the vertical plane for a supporting frame and serveprimarily as supports for the sheetmetal panels which constitute thevehicle's load surface.

The loadbearing structure has a load surface arranged on its top side.The upper horizontal wall element may preferably consist of corrugatedsheetmetal which, according to a further embodiment, may have a planarpanel arranged permanently on its top side. The result is a structurewith great shear resistance which at the same time provides a loadsurface on the top of the panel. Such a panel may be of metallicmaterial such as aluminium or, for example, wooden material such asplywood.

In accordance with the process for manufacture of a loadbearingstructure for heavy vehicles according to the present invention, theconstituent wall elements of the box-shaped unit are made of thinsheetmetal material. The wall elements may have dividing lines in boththe transverse and longitudinal directions of the vehicle and befastened along them at every second one to form a torsion-resistantbox-shaped unit. The wall elements may be manufactured by a simplerolled forming process or by rolling mill forming. Said load surface,preferably made of corrugated sheet steel, may also be manufactured byrolled forming.

According to a preferred embodiment, the assembly of the loadbearingstructure according to the present invention involves first fitting oneor, advantageously, a multiplicity of supporting frame structures to thebottom wall element. Thereafter, suspension devices and other vehiclecomponents which are to form part of the box-shaped unit are fitted tothe supporting frame structures before the L-shaped elements arefastened to the supporting frame structures to form the box-shaped unit.Thereafter, preassembled vehicle components such as wheel shafts,gearbox, engine and cab body are fitted to the suspension devices beforethe supporting devices and their load surface are fitted. Manufacturemay take place in large sections and in modules which substantiallysimplify assembly and disassembly. When components in the box-shapedunit have to be serviced or repaired, only a bottom wall element need beremoved.

DESCRIPTION OF THE DRAWINGS

The invention is described below in the form of a non-limitativeembodiment according to the present invention, with reference to theattached drawings, in which:

FIG. 1 depicts in a partly sectioned perspective view a schematicdiagram of a heavy vehicle and its loadbearing structure according tothe present invention,

FIG. 2 shows in perspective the constituent elements of a loadbearingstructure according to the present invention, separated from oneanother,

FIG. 3a shows an end view of a loadbearing structure according to thepresent invention,

FIG. 3b shows in sectioned perspective an enlargement of a view A inFIG. 3a,

FIG. 3c shows in cross-section an enlargement of a detail B in FIG. 3a,

FIG. 3d shows in plan side view a supporting frame structure for theloadbearing structure and

FIG. 3e shows in plan side view a supporting device for the loadbearingstructure.

DESCRIPTION OF AN EMBODIMENT

FIG. 1 shows a schematic diagram of a heavy vehicle and its loadbearingstructure 2, with a load surface 4 preferably incorporating underlyingcorrugated thin sheetmetal 18,31 and a panel 35 arranged on thesheetmetal. Advantageously the panel may be divided into a number ofsections, as shown in the drawing. The loadbearing structure 2incorporates a hollow box-shaped unit 10 (hereinafter called the box 10)extending in the longitudinal direction of the vehicle, and a number ofsupporting devices 30 connected externally to it.

As may be seen in FIG. 2, the loadbearing structure is made up of wallelements 12,14,16 and 18 which form the box 10. FIG. 2 shows theconstituent elements of the loadbearing structure 2 somewhat separatedfrom one another for the sake of simplification. A bottom wall element16 is connected to a multiplicity of supporting frame structures 20(hereinafter called supporting frames 20) distributed along the box 10,to which a multiplicity of supporting devices 30 likewise distributedalong the box 10 are also connected. FIG. 2 shows only one supportingframe 20 and one supporting device 30 and also shows both of themincorporating apertures for accommodating weight- and strength-optimisedsupporting frames 20 and supporting devices 30 respectively. Thesupporting devices and the supporting frames are each advantageouslymanufactured integrally in the form of a homogeneous frame 20, which isadvantageously made of aluminium by die-casting or of pressed andstamped sheet steel.

An overlying surface portion 31 is arranged on top of the supportingdevices 30 and the box 10. The surface portion 31 may advantageouslyconsist of corrugated sheetmetal 18,31 and form a foundation for a loadsurface/load platform.

The box 10 may, as depicted in FIG. 2, consist of an upper roof wallelement 18 arranged horizontally, a lower bottom wall element 16 and twovertical wall elements 12,14. The wall elements 12,14,16,18 havedividing lines primarily in the longitudinally direction of the vehicleand are intended to be fastened to each other along them to form atorsion-resistant box 10.

The vertical wall elements 12 and 14 are each connected at theirrespective upper ends to horizontal wall portions 19 and 19′respectively which form substantially the whole of the horizontal roofwall element 18. Each wall element 12 or 14 forms together with therespective wall portion 19 or 19′ a single L-shaped unit which canadvantageously be manufactured and formed integrally. The two separateL-shaped units 12,19 and 14,19′ respectively are brought together atassembly stage and fastened to one another, e.g. by spot welding, toform a single unit incorporating vertical wall elements 12,14 and ahorizontal roof wall element 18. The wall elements 12,14 and 18 may ofcourse be made up of several smaller wall elements in the form oflaid-on pieces of sheetmetal or the like joined together to form acomplete wall element. Advantageously, the horizontal wall elements maybe of corrugated sheetmetal while the vertical wall elements aresubstantially planar. In case of need, the planar vertical wall elementsmay in particular be provided with recesses and apertures through whichcomponents and connections between them may extend.

FIG. 3a shows an end view of the loadbearing structure according to thepresent invention incorporating the box 10 composed of the wall elements12,14,16 and 18, a supporting frame 20 and, firmly connected to theoutside of the box 10, supporting devices 30. FIG. 3a also shows how theload surface 4 consists of the panel 35 arranged on the corrugatedsheetmetal 18,31.

The supporting frame 20 incorporates two parallel vertical leg elements24,28 situated at a distance from one another, and horizontal upper andlower leg elements, 22 and 26 respectively, between which a centralaperture 21 is formed. The supporting frame may have a substantiallyrectangular or, with advantage, a square cross-section. For a heavy-dutyfreight vehicle, the sides of the box 10 and hence of the supportingframe 20 may typically be between about 900×900 mm and about 700×700 mmand, with advantage, about 800×800 mm.

The vertical wall elements 12,14 of the box 10 have the supportingdevices 30 arranged on their outside, firmly connected to the box 10 atits upper portion 13 and its lower portion 15. Advantageously therespective supporting devices 30 are fastened to and situated in thesame vertical plane as a supporting frame 20 arranged in the box 10. Theconnection between the supporting frames 20 and the supporting devices30 is advantageously of the riveted or threaded connection type and thefact that the transmission of forces between them takes place via theintermediate wall element sheetmetal 12,14 results in the creation of aparticularly torsion-resistant box 10. Each supporting device 30 has ahorizontal leg element 32, a first diagonal leg element 34 and a seconddiagonal leg element 36 which extend substantially transversely to theextent of the box 10 in the longitudinal direction of the vehicle andsubstantially horizontally out from the box 10. The supporting device 30is also of small extent in the longitudinal direction of the box 10relative to that in its transverse direction, and said extent is withadvantage substantially the same as that of the respective supportingframe 20.

The horizontally arranged leg element 32 of the supporting device 30 iswith advantage designed as support for the overlying load surface 4.This results in a substantial advantage of the present invention in thepossibility of creating a load surface integrated with the whole vehicleframe. Such a load platform also forms a substantial part of aloadbearing and torsion-resistant structure for the vehicle. Thediagonal leg element 34 is force-absorbingly connected to the box 10 byone end of the leg element 34 being joined to the lower portion 15 ofthe respective vertical wall element and more specifically to thesupporting frame 20 situated in the same vertical plane. The other endof the leg element 34 is adjacent to the outer end of the horizontal legelement 32 at a formed edge portion 38. One end of the diagonal legelement 36 is connected to the upper portion 13 of the respectivevertical wall element and is more specifically connectedforce-transmittingly to said supporting frame 20 situated in the samevertical plane. The other end of the leg element 36 has a lower endportion which is directed along the vehicle and which serves asfastening points for, for example, side underrun protection (notdepicted) placed along the vehicle.

The outer edge portion 38 of the leg element 32 serves as a supportingcontact surface for a supporting member which is arranged in thelongitudinal direction of the vehicle and which may be seen in moredetail in FIG. 3c below. The edge portion 38 also has, with advantage, adesign which is adapted to accommodate a formed fold (or a corrugation)of the overlying corrugated sheetmetal 31, whereby the edge portion thusserves to secure the sheetmetal.

FIG. 3b shows an enlargement of a view A in FIG. 3a. The vertical wallelement 14 is firmly arranged to the lower bottom wall element 16 bymeans of a stiffening connection 39 in the form of a joint in thelongitudinal direction of the vehicle. This connection may for examplein certain sections/modules of the box 10 be of the spot weld or rivetedtype, but may also for certain other applications be entirely of thereleasable connection type such as a threaded connection. This lattercase thus makes it possible, when necessary, to remove one or morebottom wall elements in order to facilitate the servicing or repair ofcomponents situated in the box 10. The connection 39 extendsadvantageously along the whole of he sides of the box 10 and has, facingaway from the box, a flange 40 which protrudes along the whole joint andis formed by the joined wall elements 14,16.

An enlargement of a detail B in FIG. 3a appears in FIG. 3c, which showsin section a supporting member 50 which is fastened by welding, rivetingor threaded connection to a formed edge portion 38 of the respectivesupporting device 30 and along the whole outer edge 37 of the loadsurface 4. The supporting member 50 incorporates a vertical portion 52and, extending perpendicular from the latter, an upper horizontalportion 54 and a lower horizontal portion 56. The upper horizontalportion 54 is provided at its outermost part with a flange-formingportion 58 intended to be fastened to the whole outer edge 37 of theload surface 31. The supporting member 50 thus helps to provide thestructure according to the invention with further rigidity.

The first step in assembling the loadbearing structure for a freightvehicle according to the present invention is to fit one and,advantageously, a multiplicity of supporting frames 20 to the bottomwall element 16, which is with advantage divided into a number ofsections, whereby said supporting frames 20 and bottom wall elementsections will form a lower box element. Advantageously, fitting to thebottom wall element 16 is carried out, as mentioned above, by releasableconnection, e.g. threaded connection, at least several supporting frames20. This is followed by fitting to predetermined supporting frames 20vehicle components (not depicted) intended to be more or less enclosedin the box 10, such as brake valves and brake cylinders, suspensiondevices for wheel shafts, engine, gearbox, vehicle bodywork (the truckcab) etc. At a subsequent stage the mutually preassembled L-shapedelements 12,19 and 14,19′ respectively are brought together and fastenedto the supporting frames and bottom wall element sections situated inthe lower box element to form the torsion-resistant box 10. This createsa protected environment for the vehicle components such as engine,gearbox, steering gear and brake cylinders which can to a greater orlesser extent be fitted inside the box 10. Fastening to the supportingframes is advantageously done by spot welding or seam welding, butriveting, nibbling or threaded connections may also be used in whole orin part. Releasable threaded connections are advantageous forconnections to the removable bottom elements 16. Thereafter thesuspension elements are used for fitting said wheel shafts, engine,gearbox and vehicle bodywork in the thus assembled box 10. Finally, eachof the supporting devices 30 may also be fastened, by any of theaforesaid means, to the respective supporting frame 20, followed by theload surface 31,35 and any side underrun protection and the like beingfastened to the support devices 30 and the roof wall element 18 of thebox 10.

The above-mentioned suspension elements are shown schematically atreference 60 in FIG. 1. A substantial advantage of the invention is thatit makes it possible to manufacture the box's wall section wall elementsand load surface elements, both corrugated and uncorrugated, in largesections and modules by simple and inexpensive conventional rolledforming or rolling mill forming processes. For application on a heavyfreight vehicle, the wall thickness of sheet steel of this type may beabout 5 mm or less. It is advantageous to use a wall thickness ofbetween about 2.0 mm and 3.5 mm. Should sheet aluminium be used, thethickness will of course be greater, of the order of about 5 to 7 mm. Ina preferred embodiment, aluminium is used in supporting frames andsupporting devices, while sheet steel electrically galvanised for thepurpose is used for the wall elements. The screws/bolts and rivets usedfor connecting these elements to one another must also be electricallygalvanised for corrosion reasons. Both the assembly of the vehicle andits loadbearing structure, including the box, and their disassembly maybe substantially simplified by appropriate modular division.

What is claimed is:
 1. A loadbearing structure for a freight vehicle,wherein the vehicle has a longitudinal direction and a transversedirection, the structure comprising: a hollow box extending in alongitudinal direction of the vehicle comprising a plurality of wallelements comprised of a material of small wall thickness and assembledand connected to each other to form said hollow box, at least one ofsaid wall elements being made of corrugated sheet material; one of thewall elements is a bottom wall element at a bottom of the box, and thebottom wall element is divided into a plurality of sections along thelongitudinal direction of the vehicle.
 2. The loadbearing structure ofclaim 1, further comprising a supporting frame structure disposed insidethe hollow box, the wall elements having an interior and the supportingframe structure being connected to the interior of the wall elements. 3.The loadbearing structure of claim 2, wherein the connections betweenthe supporting frame structure and at least some of the sections of thebottom wall element are releaseable for enabling removal.
 4. Theloadbearing structure of claim 1, wherein the wall elements include abottom wall element at a bottom of the box; the wall elements having aninterior; a supporting frame disposed inside the hollow box, and thesupporting frame structure being connected to the interior of at leastthe bottom wall element.
 5. The loadbearing structure of claim 4,wherein the supporting frame structure comprises a plurality of frameslocated at spaced intervals along the longitudinal direction inside thehollow box.
 6. The loadbearing structure of claim 5, wherein each of thesupporting frames extends substantially vertically and transverse to thelongitudinal direction of the vehicle.
 7. The loadbearing structure ofclaim 6, wherein each of the frames has an aperture through it openingthe frame along the longitudinal direction of the vehicle.
 8. Theloadbearing structure of claim 6, wherein each of the frames is anintegrally formed frame separate from the box and located in the box,the frame having substantially a square shape and a central aperturewhich opens along the longitudinal direction of the vehicle with theframe installed in the box.
 9. The loadbearing structure of claim 6,wherein the bottom wall element is divided into a plurality of sectionsalong the longitudinal direction of the vehicle.
 10. The loadbearingstructure of claim 2, further comprising the wall elements of the boxincluding vertically arranged wall elements each having an externalside; supporting devices disposed outside the external sides of thevertical wall elements, the supporting devices extending transversely tothe longitudinal direction of the vehicle and the supporting devicesincluding force transmitting connections to at least one of the supportframe and the respective one of the side walls where the supportingdevice is located.
 11. The loadbearing structure of claim 10, whereineach of the support devices includes an upper horizontal leg and adiagonal leg oriented to intersect the horizontal upper leg.
 12. Theloadbearing structure of claim 10, wherein the supporting framestructure comprises a plurality of frames located at spaced intervalsalong the longitudinal direction inside the hollow box: each of thesupporting devices is disposed along the longitudinal direction of thevehicle in the same plane as one of the supporting frames and transverseto the longitudinal direction of the vehicle; one end of the diagonalleg element being supportingly connected to a lower portion of therespective support frame in the respective plane.
 13. The loadbearingstructure of claim 10, wherein the box includes an upper horizontal wallelement; the upper horizontal leg of the supporting device is positionedtogether with the upper horizontal wall element of the box to form anoverlying surface adapted for supporting a load.
 14. The loadbearingstructure of claim 1, wherein the material of the wall elements is athin sheet metal.
 15. The loadbearing structure of claim 1, wherein thematerial of the wall elements is a thin sheet steel.
 16. A loadbearingstructure for a freight vehicle, wherein the vehicle has a longitudinaldirection and a transverse direction, the structure comprising: a hollowbox extending in a longitudinal direction of the vehicle comprising aplurality of wall elements comprised of a material of small wallthickness and assembled and connected to each other to form said hollowbox; wherein one of the wall elements is a bottom wall element at abottom of the box, and the bottom wall element is divided into aplurality of sections along the longitudinal direction of the vehicle;and wherein the wall elements include two opposite, parallel, L-shapedcross section, longitudinally extending wall elements; each wall elementincluding one leg arranged substantially vertically, and thesubstantially vertically extending legs of the L-shaped cross sectionwall elements are spaced apart; and each L-shaped cross section wallelement including a horizontal leg which meets the horizontal leg of theother of the L-shaped cross section wall elements forming an upperhorizontal wall element of the box.
 17. A loadbearing structure for afreight vehicle, wherein the vehicle has a longitudinal direction and atransverse direction, the structure comprising: a hollow box extendingin a longitudinal direction of the vehicle comprising a plurality ofwall elements comprised of a material of small wall thickness andassembled and connected to each other to form said hollow box; whereinone of the wall elements is a bottom wall element at a bottom of thebox, and the bottom wall element is divided into a plurality of sectionsalong the longitudinal direction of the vehicle; a supporting framestructure disposed inside the hollow box, the wall elements having aninterior and the supporting frame structure being connected to theinterior of the wall elements; the wall elements of the box includingvertically arranged wall elements each having an external side;supporting devices disposed outside the external sides of the verticalwall elements, the supporting devices extending transversely to thelongitudinal direction of the vehicle and the supporting devicesincluding force transmitting connections to at least one of the supportframe and the respective one of the side walls where the supportingdevice is located; wherein the box includes an upper horizontal wallelement and the upper horizontal leg of the supporting device ispositioned together with the upper horizontal wall element of the box toform an overlying surface adapted for supporting a load; and a loadsurface of corrugated sheet metal extending over the upper horizontalleg of the supporting device and the upper horizontal wall element ofthe box.
 18. A process for manufacturing a load bearing structure for afreight vehicle wherein the loadbearing structure includes a pluralityof wall elements which form a box that extends in the longitudinaldirection of the vehicle and which is hollow, the process comprising:providing sheet metal material of thin wall thickness; formingrespective wall elements for the box from the sheet metal material,fastening the wall elements to each other along dividing lines extendingalong the longitudinal direction of the vehicle so that the hollow boxhas adequate torsional rigidity for loadbearing in a vehicle, at leastone of said wall elements being made of corrugated sheet material; thebox includes a bottom wall element, a top wall element and side wallelements, and the process comprises applying each of a plurality ofsupporting frames to the bottom wall element at spaced intervals alongthe longitudinal direction of the vehicle; fitting vehicle components inthe form of suspension devices through the supporting frames on thebottom wall elements; applying the bottom wall element, the top wallelement, and the side wall elements together and fastening them to thesupporting frames and to the bottom wall elements to form a torsionresistant box.
 19. The process of claim 18, further comprising attachingpre-assembled vehicle components to pre-selected suspension devicesfastened to the supporting frames.
 20. The process of claim 18, whereinthe bottom wall is produced by providing individual separate bottom wallelements; arranging the bottom wall elements in a row in a longitudinaldirection of the vehicle; and connecting respective supporting framesbeing connected to at least some of the individual bottom wall elementsections.